Gas separation is useful in many industries and can typically be accomplished by flowing a mixture of gases over an adsorbent material that preferentially adsorbs one or more gas components while not adsorbing one or more other gas components. The non-adsorbed components are recovered as a separate product.
One particular type of gas separation technology is swing adsorption, such as temperature swing adsorption (TSA), pressure swing adsorption (PSA), partial pressure swing adsorption (PPSA), rapid cycle pressure swing adsorption (RCPSA), rapid cycle partial pressure swing adsorption (RCPPSA), and not limited to but also combinations of the fore mentioned processes, such as pressure and temperature swing adsorption. As an example, PSA processes rely on the phenomenon of gases being more readily adsorbed within the pore structure or free volume of an adsorbent material when the gas is under pressure. That is, the higher the gas pressure, the greater the amount of readily-adsorbed gas adsorbed. When the pressure is reduced, the adsorbed component is released, or desorbed from the adsorbent material.
The swing adsorption processes (e.g., PSA and TSA) may be used to separate gases of a gas mixture because different gases tend to fill the micropore of the adsorbent material to different extents. For example, if a gas mixture, such as natural gas, is passed under pressure through a vessel containing an adsorbent material that is more selective towards carbon dioxide than it is for methane, at least a portion of the carbon dioxide is selectively adsorbed by the adsorbent material, and the gas exiting the vessel is enriched in methane. When the adsorbent material reaches the end of its capacity to adsorb carbon dioxide, it is regenerated by reducing the pressure, thereby releasing the adsorbed carbon dioxide. The adsorbent material is then typically purged and repressurized. Then, the adsorbent material is ready for another adsorption cycle.
The swing adsorption processes typically involve adsorption units, which include adsorbent bed units. These adsorbent bed units utilize different packing material in the bed structures. For example, the adsorbent bed units utilize checker brick, pebble beds or other available packing. As an enhancement, some adsorbent bed units may utilize engineered packing within the bed structure. The engineered packing may include a material provided in a specific configuration, such as a honeycomb, ceramic forms or the like.
Further, various adsorbent bed units may be coupled together with conduits and valves to manage the flow of fluids. Orchestrating these adsorbent bed units involves coordinating the cycles for each of the adsorbent bed unit with other adsorbent bed units in the system. A complete cycle can vary from seconds to minutes as it transfers a plurality of gaseous streams through one or more of the adsorbent bed units.
Unfortunately, conventional swing adsorption processes have certain limitations that are inefficient or do not operate properly for purging the contaminants from the adsorbent beds. That is, the conventional adsorbent bed units provide gas streams from one end or the other end of the adsorbent bed. The purging in conventional systems is time consuming and can be inefficient. For engineered packing, the structure of the bed further complicates the purging of fluids from within the engineered packing if the adsorbent bed is formed into a specific configuration.
Accordingly, there remains a need in the industry for apparatus, methods, and systems that provide an enhanced adsorbent bed unit. The present techniques provide a method and apparatus that overcome one or more of the deficiencies discussed above. In particular, the present techniques provide an adsorbent bed unit that includes a mid-bed purge system that enhances the operations of the swing adsorption processes to provide gas from a location other than the end of the adsorbent bed.